Nearly three weeks after Hurricane Maria devastated the U.S. territory of Puerto Rico, more than 80 percent of the island remains without power, business has come to a standstill, and residents are drinking from streams.

Arelis R. Hernandez and Joel AchenbachWashington Post

After Hurricane Irma swept through the Caribbean last September, federal officials in Puerto Rico began shipping disaster relief supplies to the hard-hit U.S. Virgin Islands. The warehouse in Puerto Rico was emptied of tarps and cots. Almost all the blue roof sheeting was dispatched, along with 90 percent of the water and the majority of the emergency meals.

In an after-action report released late Thursday, the Federal Emergency Management Agency exposed its failure to be prepared for what nature delivered to Puerto Rico last year. The government had anticipated dealing with one hurricane, not two.

"Existing plans were developed for the occurrence of a single incident, rather than concurrent incidents," the report states.

This failure of imagination became clear when, two weeks after Irma's near miss of Puerto Rico, Maria caught the island flush, obliterated the electrical grid, shut down the cellphone network, closed ports and airports and killed a still-unknown number of people. The 3.5 million island residents were forced to survive in primitive conditions with a fraction of the disaster assistance available to other Americans who had been hit by hurricanes in Texas and Florida.

The new report acknowledges that federal officials in Puerto Rico had a lack of "situational awareness" - meaning they didn't know what was happening across the island, nor how to address the rapidly developing humanitarian crisis.

The hypothetical hurricane FEMA planners had anticipated and prepared for in recent years was far less destructive than the one that arrived on Sept. 20. FEMA envisioned a storm knocking out power to 73 percent of the population, the report states. Maria destroyed the entire grid - much of it for months.

The hypothetical storm would require search and rescue resources across 75 percent of the island. Maria required search and rescue for 99 percent.

The plan imagined that 56 percent of hospitals would be affected. The reality was 92 percent.

FEMA on Friday defended its efforts, saying it faced unprecedented challenges when hurricanes Harvey, Irma and Maria roared through the Caribbean in rapid succession during a few weeks in August and September.

"I do think we were prepared," FEMA associate administrator Jeff Byard said Friday in an interview at agency headquarters in Washington. "We didn't fail."

Byard said that the public must take the totality of the circumstances into consideration. He said the agency faced multiple distinct disasters, with Puerto Rico presenting a "unique challenge."

After FEMA sent supplies from Puerto Rico to the U.S. Virgin Islands, he said, the agency started restocking the warehouses on Puerto Rico. Then Maria cut off the shipping lines.

For the U.S. disaster response to be successful, Byard said, all levels of government and the private sector have to work together. That didn't happen in Puerto Rico because of communication failures. He said it was unclear if the territorial government even had a disaster plan.

"I don't want to say they didn't have a plan," Byard said. "But I didn't see a plan."

The new FEMA report examined all the hurricanes of 2017, which resulted in hundreds of billions of dollars in economic damage and led to nearly 5 million applications from individuals for federal disaster assistance. The Government Accountability Office plans to issue its own report in August. Democrats in Congress have unsuccessfully pushed for an independent review of the federal response.

FEMA's report was met Friday with a collective shrug from Puerto Rican leaders, who said the agency's shortcomings already were glaringly obvious. Across Puerto Rico, about 2,000 customers still don't have electricity running into their homes, and thousands live in roofless houses covered by decaying blue tarps.

Water service has returned, but it depends on an unreliable power grid to keep flowing. Many families who applied for disaster aid to rebuild their homes are still waiting for the money.

"It's great that they are finally saying it," said Jesús Colón Berlingeri, the mayor of Orocovis, a town in Puerto Rico's central mountains. "But we still feel there isn't a sense of urgency to solve problems."

Rafael Surillo, the mayor of Yabucoa, near where Hurricane Maria made landfall on the island's southeast corner, said of FEMA: "They had nothing prepared and they are still failing."

Surillo said if he had waited for FEMA to supply the generators to power water pumps in his city of 35,000, his people would not have had water for more than two months. The mayor said a local businessman used connections on the mainland to ship generators to Yabucoa.

The aftermath of Maria has incited anger among storm survivors who blame the Trump administration for what they see as a feeble response, and they blame President Donald Trump personally for what they saw as callousness after the storm's landfall.

"It's really just a part of a pattern where the rhetoric of the administration affects the priority and urgency put forward by a government agency," said Federico de Jesús, co-founder of BoricuActívatEd, an advocacy group for Puerto Ricans in the diaspora.

Trump engaged in a running Twitter debate with the mayor of San Juan - Carmen Yulín Cruz - who was furious at the slow disaster response. During a visit to the island soon after the storm hit, Trump scored few points among residents by flipping rolls of paper towels to survivors. He has downplayed the death toll, described Puerto Ricans as overly needy and said falsely that Maria was not a disaster on the scale of Hurricane Katrina.

This new report by FEMA offers details about the chaos and confusion of those first days and weeks after Maria hit the island. With power out and the cellphone network largely destroyed, FEMA was operating in the dark. A week after the storm hit, FEMA and its partners didn't have any information on the status of nearly half of the 52 waste water treatment plants on the island and more than half of the 69 hospitals, the report states.

The agency lost track of supplies as they went to Puerto Rico. FEMA blames communications challenges and lack of trained staff to monitor the movement of supplies.

Puerto Rico lagged far behind Texas and Florida when it came to FEMA personnel on the ground. Within a week after Harvey made landfall in Texas, FEMA had about 5,000 people deployed there. But Puerto Rico, a thousand miles from the mainland and further isolated by the closing of ports and airports, received a relative trickle of emergency responders at first. A month after Maria hit, FEMA deployments to Puerto Rico had risen only to roughly 2,000 personnel, far less than the number still in Texas and Florida.

FEMA was not fully staffed in 2017. In the desperate conditions of Puerto Rico, FEMA resorted to giving staff members what could be described as battlefield promotions. These promotions "placed staff in positions beyond their experience and, in some instances, beyond their capabilities," the report states.

Puerto Rico's poor infrastructure, economic misery and cuts to emergency preparedness programs before Maria impeded the recovery effort, the report states, but the agency admits that it should have foreseen how badly a big storm would damage Puerto Rico and the U.S. Virgin Islands.

"FEMA leadership acknowledged that the Agency could have better anticipated that the severity of hurricanes Irma and Maria would cause long-term, significant damage to the territories' infrastructure," the report states.

Rep. Nydia Velázquez, D-N.Y., said the report shows FEMA was "profoundly unprepared for Maria, its response was hobbled by incompetence and a lack of leadership and, tragically, the people of Puerto Rico suffered because of it."

In the mountain town of Orocovis, Berlingeri's workers have patched roads, but funding for their long-term safety has not yet been disbursed, he said. "The people perceive that they don't care about us," Berlingeri said.

Josian Santiago, the mayor of Comerio, said he has more than 200 families living in homes where tarp is the only thing between their heads and the weather. He complained that FEMA has not released the funds he needs to pay contractors who cleared debris and roads 10 months ago. If they aren't paid soon, he said, he can't count on their help if another storm arrives this summer.

And it is hurricane season again. Santiago said his request to commonwealth authorities and FEMA for a generator and supplies to get it ready have yielded nothing.

"They didn't even try to work with us," Santiago said.

Byard, of FEMA, said the agency has trained hundreds of residents as emergency managers to fill in gaps. The report includes many recommendations for improvement, including increasing the amount of relief supplies staged in remote locations, and being better prepared to deploy staff members to disaster zones.